In a pistol of the prior art, a single-used gas bottle is generally used to be vertically mounted in a magazine which is fixedly mounted in the pistol, and thus the gas inside the gas bottle is directly supplied to the pistol. However, when using the pistol of this type, the pressure of the gas is instable, which results in a discontinuous gas supply. Besides, the gas can not be used up, a part of the gas is wasted, and thus the gas has a low utilization. Furthermore, the magazine can not be portable and can not be further removed after it is mounted in the pistol. When the gas is substantially used up, the magazine needs to be opened to take out the old gas bottle, and further insert a new one. Therefore, the replacement of the gas bottle is complicated and inconvenient.